we live in a detached property with a small coservatory on the property boundary, from the neighbours side it appears the brick work is not keyed into the main wall although i have not identified if wall plates where used, my neighbours are just starting to build a extension and have passed a letter to us stating they are digging there foundations and there is a possability the conservatory wall may become unstable, question if this does happen is it there builders responsability to correct any damage that may accure even if the wall is not keyed in
thanks

you need to tell them that you are going to apoint a Party Wall surveyor, at there cost, under the Party wall Act.

they have to put forward proposals to your surveyor who will appoint a structural engineer to comment/approve before any work takes place. all at there cost, else you can have a court injunction put on them to stop work.
look one up in the yellow pages.
regards
andy

Andysarah is right. If your neighbour is excavating within 3m of your property and to a depth assumed to be greater than your own foundations, they will need to serve a 3m notice under S6 of the Party Wall etc Act 1996. You have the right under this act to appoint your own surveyor to ensure that works are carried out that will not cause detriment to your wall or strucutre. Fees for the appointment of a surveyor normally (but not always) fall with the person carrying out the works (S11). If you do not respond to the notice, it is deemed that you have dissented from the works. They can then issue a letter requesting that you appoint a surveyor within 10 days of that letter or thay can make an appointment on your behalf.

Court injunctions can certainly be obtained, but can be very expensive, due to the need to have barrisers etc to had. My advice would be to find a local Chartered Building Surveyor (doesn't need to be mind) familiar with party wall proceedures who can attend to it for you.